Hard materials are generally not tough but they are brittle. The failure mechanism consists of crack initiation, mostly at dislocations, and crack propagation. In the present invention, new materials are disclosed which affects crack stopping and therefore leads to materials which are both hard and tough. The materials include a lamination of hard and tough materials in the form of thin films (superlattice). A crack initiated in any hard layer of the superlattice will stop when it reaches the tough layer. In a hard material, the crack will propagate all the way through. As used herein, a superlattice means a superposition of a different periodicity on to the lattice structure of the individual materials.
Multi-layer structures consisting of either pure metallic systems, such as Cu-Ni etc. , or semiconductive systems such as GaAs-AlAs, have been widely studied. However, until the present invention, superlattices between hard refractory metal carbides and tough transition metals have not been studied.